HoBao Hyper ST Truggy Pro

[Rustypeb89]

Couldn't get out yesterday due to work but getting the car ready today i found I couldn't prime the engine by having my finger over the exhaust and turning the engine over so took the fuel line off the exhaust and blew down it and had air coming out of the lid for the fuel tank, when i held that down the fuel went to the engine fine. So will order a new fuel tank but also wondering if that might have also been causing me problems before and not getting enough fuel to the engine all the time. Will find out when i get a new tank or work out a way to hold this one down better.

 

[Rustypeb89]

Managed to hold the lid down with some cable ties but of a pain tho as can't refuel. 

It started very easily and idled nicely for over a minute with out any throttle so happy with that.

I used half a tank warming the engine and tried some WOT passes and ended up richening the HSN to get the idle to drop after. Think I ended up with it quite rich but that's better then lean.

Got a quick video, you will have to excuse the bad filming trying to drive and film was harder then I thought. Was on about quarter of a tank here. The highest the engine temp got was 190f 

Might have anouther play after I have got some jobs done. 

Edited January 29, 2017 by Rustypeb89

[atom3624]

Sounds good - I miss the 'nitro sound'.

Nice enough idle for me - sounds stable and little / no sign of 'creep'.

 

Is there a 2-speed you can get for them at all - never like to hear an engine maxing for a long period.

 

190F is good.

 

Al.

[capri-boy]

38 minutes ago, atom3624 said:

Sounds good - I miss the 'nitro sound'.

Nice enough idle for me - sounds stable and little / no sign of 'creep'.

 

Is there a 2-speed you can get for them at all - never like to hear an engine maxing for a long period.

 

190F is good.

 

Al.

 

There's a 2 speed available for the H7, and as such the gearing will be unsuitable for the ST.  Just as relevant though it replaces the centre diff, so a backwards step for an offroader.

 

 

[atom3624]

Pity.

Agreed with the need for a centre diff.

Al.

[Rustypeb89]

1 hour ago, atom3624 said:

Sounds good - I miss the 'nitro sound'.

Nice enough idle for me - sounds stable and little / no sign of 'creep'.

 

Is there a 2-speed you can get for them at all - never like to hear an engine maxing for a long period.

 

190F is good.

 

Al.

Thanks, yeah these is quite new to me and completely different to the electric I used to drive. Seems more involved too which I'm enjoying. 

Thats good this Video was taken after a bit of playing but happy how it is going sure the engine can give some more but want to take it slow as I'm learning it. 

 

Not it a clue but I understand what you mean doesn't sound right having it screaming for too long. Sure there fine tho. 

 

Thats good just just taken it out again in the rain :/ but had 3 tanks through it and the highest temp I got was 210f. Jumped and crashed it quite hard a couple of times and nothing broken so happy with that  

[locky]

Open the throttle whilst priming and see if that makes any difference in fuel flow.

 

Regarding fuel cap leak, there is a screw on the underside of the cap, try tightening this as it should squash the o-ring wider and help the seal. Dont think you need a new tank, worst case new o-ring but shouldnt as it's a new kit.

 

Tuning sounds good all way through rev range.

[Rustypeb89]

Thanks will give that a try. 

 

Ah ok will try tightening that, did also read there known for leaking a bit there so don't want to buy a new one for it to just do the same. Saying that the 3 tanks I put through it after the video the lid wasn't held down and didn't have any problems just pushed the lid down whilst I primed it. 

 

Thats good think I'm starting to understand it a bit. 

 

Thank you you for all your help so far. 

[locky]

A different way of tuning and some good explanations...

 

Tuning a LRP 30 the Nitroshop way
Here is my way to tune the LRP 30... My name is Neal Smith, I Am the owner of www.thenitroshop.com , I was formerly with Clockwork Racing Engines... I go by several names on the forums, Nitrojedi being one of them, sometimes Maximo.... Anyways I have been running nitro since 1984 and over the years become very proficient at tuning and have developed somewhat of of my system that works extremely well for short needle carbs like the LRP has... I promote tuning by sound over tuning by temperature and often times I don't even bother to use a temp gun... Once you learn what to listen for there is no better way to tune then by sound, it is without question the most accurate and consistent method.... When train yourself to listen to the engine you will find that the sounds it makes never lie, a lean engine will always sound like a lean engine no matter what the temp says..and if a engine doesn't sound lean then it isn't lean.......doesn't matter if your temp gun is telling you the engine is 400 degrees, if the engine sounds proper then it is proper.... a overheating or over lean engine will have telltale sounds that always will be present no matter what...there is no way to make a lean engine sound rich and no way to make a rich engine sound lean
So first and foremost is you need to set your idle gap size as well as make sure your linkage is functioning correctly........When I say functioning correctly I mean that when your radio is at neutral your throttle slide is closed 100%, with no further possible movement....It then has to pass the throttle down test..that where you hold full throttle then let go of the trigger, the throttle slide needs to snap shut 100%...it cannot hang open even the tiniest amount...this is non negotiable, if your linkage is not closing 100% during this test you will never be able to properly tune your engine.. So this means hold full throttle, let off the trigger....then check your slide and try to push to closed further, if you can closer it further then your linkage is hanging open.... i CANNOT STRESS TO YOU ENOUGH THE IMPORTANCE OF A PROPERLY FUNCTIONING THROTTLE LINKAGE !!!! YOUR LINKAGE MUST BE CLOSING 100% WHEN YOUR TRIGGER IS AT NEUTRAL !!!!! Do not rely on using your brakes to close the throttle slide, it has to do it at neutral with no further movement when you hit the brakes..... Also its a good idea to have some deadband on your throttle slides, meaning your throttle servo has some free play before it opens the carb slide...If your dont have any free play your throttle can get feathered opened by the servo twitching... SO always be sure there is free play in the linkage when at neutral...
So once we know your linkage is working and snapping itself *censored* we want to set a 0.5 mm idle gap...0.5 mm is the thickness of a exacto blade... if you have calipers measure a piece of wire or a needle or pin and use that as a feeler gauge to set the gap..if not look at the thickness of the X-Acto blade and use it as a guide to set your idle gap.... Even use a feeler gauge to test to make sure your linkage closes correctly...this here is without question the #1 reason most guys fail at tuning a nitro..their throttle slides are not operating perfectly and they have to large of a idle gap..... these 2 critical things are the #1 overlooked issue and the source of 1000's of phantom air leaks.......I cannot stress enought, make sure you have a 0.5 mm idle gap and that your throttle is operating correctly ! till these 2 things are absolutely perfect we cannot properly tune your engine, no ifs ands or butts about it ! your wasting your time adjusting the engines needles till you know for sure these 2 areas are correct !
So lets talk about tune shifting and how heat affects the engines tune...Many tuning guides make no mention of this and its also a huge source of tuning issues.... These engines go thru a massive tune shift as they warm up, and the hotter they get the leaner they get, as well not only that but the harder you run them the leaner they get.. A good race engine will take 10 minutes of hard driving on a track to become thermally stable and for the tune to stabilize, up until that point the tune continually shifts leaner and leaner... When first fired a properly tuned engine will be sputter rich often with a very high idle and often want to stall easily... However as you continue running the enegine the idle will start to stabilize and as you get the engine on the ground and under load you will see the tune slowly start to clear up, and the longer you run it the better and better the tune becomes, till after roughly 10 hard minutes you will have the tune right back to where you left it the day before when you tuned it.... As i say the tune shift these engines will go thru is massive, from initial fire up to final hot tune you are talking a huge shift in engine mixture....l see soo many guys tuning their engines too soon and end up with a overly lean engine once everything heat saturates...... On a race track how hard a engine is run determines the ideal needle settings... Meaning I can set the needles perfectly for a average racer and he could race all day with a perfect tune..but if i gave the same car to a faster driver the tune would very quickly become too lean as the engine is being worked harder with the faster racer.......... this holds true for your MT's...meaning the perfect tune may vary depending on what your doing with the truck and how hard you are running it..... Wide open top end runs in heavy grass is going to want a much richer needle position then popping short wheelies in your front yard...So understand that the tune is going to move around on you and thats its perfectly normal....... what your going to need to do is learn to listen to the engine and make the appropriate adjustments..... And truly once you know what to listen for its super simple to tune these engines !!!! I mean it, its really really really simple !
Idle speed ! that's right, that's what we use to tune the engine, we listen to its idle speed both when we let off the throttle as well as its idle speed after sitting still for several specific time tests...... A lean engine will always, and I mean always want to high idle ... you will do a top end pass and when you let off the trigger the engine will carry RPM before it drops down, in severe cases it will make Chewbacka sounds...What you want to happen is for the engine to drop down to idle the instant you let off the trigger, then sit at a steady idle for 1-2 seconds then to drop a slower slightly lopey idle, relaxed and almost like a Harley Davidson...A lean idle will sound like a buzzing bee, it will be steady and buzzy and have no lope to it, very not sound relaxed..... Now if your linkage is hanging open or your idle gap is too big it can simulate the lean buzzy sound....this si why soo many guys get their needles all mixxed up, as their linkage and idle gap issues are creating a false lean ( well it is actually lean due to too much air ) ................. So As I say listen to what the engine does when you let off trigger, if it carries RPM your HSN is getting too lean ( or your idle gap is is still too open ).............
On these carbs preset a 0.5 mm idle gap..use the LSN solely as a idle mixture control..meaning do not use the LSN to adjust the engines low speed performance...the LSN is to be treated only as a way to adjust the engines fuel mixture while at idle....nothing else, All performance tuning is to be done using the HSN.... if you have a rich bog out of the corner lean the HSN, if you have a lean bog off the line fatten the HSN.....do not whatever you do use the LSN for anything but idle mixture control !
Now when at idle you want the engine to have a lope to to it, not almost stalling, but with a definite and audible miss ... you want it to slowly load up the longer it idles , meaning the longer it idles the lower and lower the idle gets, eventually tot he point it will stall out, however the longer it can sit low and slow ans still stay running the better...a lean LSN Will never allow this to happen..if the LSN is lean the engine will always have a steady buzzy idle and will not load up just sitting there idling.... when I tune a engine I continually check the idle, how it idles, how it idles down and how long it takes to load up........ Always listening for a fast idle down to a slow steady idle then a quick transition down to a slower lopey idle............... A lean engine will never be able to properly idle down..if the HSN is too lean it will carry RPM and if the LSN is too lean the idle will stay high and buzzy............ most videos I see online have a high buzzy lean idle......
So when I tune I baseline a 0.5 mm idle gap, I fire the engine, adjust the LSN to get a reasonable starting point for idle speed, then I fatten the top end till she sputters and then run by run slowly lean it down..little by little I lean down the top end always double checking my idle down then idle speed.... as I approach the engines sweet spot I make finer and finer adjustments, till the point I am only moving the needle a hair, like 1/48th of a turn.... when your near the sweet spot a 1 hour movement is too much..... as the closer you are the sweet spot the more sensitive the needles become.... So I basically lean my HSN till I start to notice the idle hanging when I let off, then I slowly fatten it back up till it goes away.... I do run after run after run always checking to make sure the engine idles down correctly and steps down to the correct idle stages..... it never lies, if the engine idles down cleanly then steps to a low slow idle you are not lean, no matter what the temp gun says..and visa versa, if your idle hangs and your engine does not step down you are lean, no matter what your temp gun says.....
Once you hae your tune set to where you think its close start doing some tests...first test is to do a wide open pass, bring the car to a abrupt stop..let the engine idle down to its second stage loping idle, then as soon is you hear it step down crack full throttle....If your are lean the engine will give you a lean bog right here... So if you get a lean bog fatten the HSN....retry the test till you can do a rapid throttle pull from a fast top off wide open............. then do this same test but doing a 3 count, then the same test with a 6 count, then a 10 count........ Once you are fully heated up you would like to see a slight loadup when you allow for a 6-10 second stop... not anywhere near enough to stall the engine, but a slight gurgle with extra smoke cloud is what we are after..........
So this is really it..listen to how the engine idles down..a properly tuned engine will idle down instantly, then quickly step from a smooth slow idle down to a slightly slower lopey idle...a lean HSN engine will always carry RPM and will want to idle high and idle will stay buzzy if the LSN is too lean....
Anyways coffee break and time to watch some TV..hopefully i dont have to many spelling issues
30% tunes easier then 20% runs cooler
lower oil tunes easier then higher oil, runs cooler and prefers a richer mixture..
I run 30/7 and it has a huge tuning window and can be run much richer then a fuel that is 20/14 , this is why the 30/7 fuel ends up performing much better and still protecting better then the 20/14...to get the 20/14 to run proper and crispy it needs to be run much leaner with a much hotter burn then what the 30/7 needs......I know this is backwards to common knowledge but is indeed accurate...

Listen to tune on this engine here for reference

https://www.youtube.com/watch?v=WgJR87HcRTE

[Rustypeb89]

Thanks Locky thats very informative will have to read through it a few times to get it all to sink in.

 

I managed to get out for a little bit today after work before it got dark, put 4 tanks through it and it all went well didn't touch the needles this time, I know it is a bit rich but happy with that for now. It needed the throttle opening with the trim to start but idled well after and once warmed up i could turn the trim to neutral and it would idle for as long as i left it. top speed and acceleration were impressive.

 

Tho now cam't wait till it has dried out a bit and i don't have to clean it quite so much at least it is easy to take apart to clean

 

I have found it hard to find replacement air filter foams so have ordered a different air filter and a load of foams for it.

Also managed to crack the body shell in a few places so going to try and reinforce that a way I have found on youtube.

 

[Rustypeb89]

From reading that and listening to the video I think i'm still too lean as my as after WOT it is still slightly holding rpm and maybe idling to fast when just sat there will have to recheck the idle gap and linkages after i have finished cleaning and make sure thats all right and see if I can have another play tomorrow. 

[locky]

For splits in body you can use dry wall mesh tape and shoe goo or E6000. Body shells dont last forever unfortunately and always best to strengthen from day 1.

 

Air filter foam can be cleaned and reoiled. Usually just the outer foam. It doesnt look too bad to me in pic. Are you running with body off most of the time?

 

I copied the tuning guide as personally thought that your idle was a bit high and HSN tadge on lean side, but it's all subjective to a degree and more important to enjoy driving, unless tinkering is your thing. 

 

A tuned engine will sound rough when started from cold until fully warmed up, so raising idle rpm is OK at beginning.

 

Main thing is getting it started and running, staying running and getting a basic tune and not shorten engine life by running too lean for too long. A hot engine runs leaner than a cold and warm engine. Running on grass makes the engine work harder than tarmac and needs different tuning.

[Rustypeb89]

Thanks, yeah that was the method I saw online. Yeah know thy went through plenty in my racing days but if I can make it take a couple more hits then all good. 

 

Yeah will I'll give this one a clean but like the idea of having some spare. That's good tho thought it was filthy lol. I have had it off for most off it but the last couple of runs where I was more bashing I had it on. 

 

Thanks it does make a lot of sense. Yeah I think you are right on my video as it comes towards me the first time you can here the rpm stays high and buzzy until I give it a little throttle, what does confuse me a bit is as I pull away after that it seems to bog down then goes again I thought this was from too much fuel getting in too rich but is this a lean bog instead? Yeah have been enjoying driving and tinkering so far but do want to do more driving then tinkering I think but want to also get the best out the engine with out shortening its life so will need to learn it all. 

 

Yeah think next time I try tuning it I will richen it out then use a tank or 2 too fully warm it up before playing with the tune. 

 

Thanks  

[Rustypeb89]

Another video this time something doesn't sound right with my steering servo like it's grinding or something? I use the throttle servo first then the steering so you can hear the difference. They are both power hd LF-20

 

Edited January 30, 2017 by Rustypeb89
Forgot the video

[locky]

Only way is take the servo apart by removing the 4 screws on the bottom and sliding the top off and then inspect the gears and bearings, remove clean and regrease.

[Rustypeb89]

Thanks, will have a look after work. Didn't notice anything driving but defiantly doesn't sound right like something is grinding or sticking. 

[Rustypeb89]

Had a look over lunch, couldn't see any thing wrong and whilst putting it back together it was quite smooth until all the gears were on olny thing i can think of is a couple of slightly damaged teeth or something tho couldn't see anything. will just carry on using it for now.  

[capri-boy]

Shameless, but have a look in the FS section - i've two of these Jconcepts shells left currently (they come clear):

 

 

(that not mine btw, a friends who had one of them)

 

Stronger imo that stock shells, but i'd still suggest drywall and shoegoo from the off - cold weather and lexan is a recipe for cracks.

 

Good to see your enjoying your ST Pro.  the LF20kg is a good servo, and i've a few in steering duties but in a 1/8 truggy there at their limit I think.  From mem replacement gear sets are available fairly reasonably, so it's always an option if it continues to get worse.

[Rustypeb89]

Thanks, will have to check it out and get one if you have one left after I get payed on Friday. They do look very nice, nicer then the stock I think. 

Thats good, yeah think I will have to do that mine has cracked in places I wasn't expecting at all. But yeah has been in cold weather and been rolled a few times so not surprising really. 

 

Thanks have been having great fun with it. Ah ok that makes sense it has a lot of stress on it I guess. Will look in to that but will probably run it until it breaks or I can afford something that isn't on its limit. Would I be after something higher the 20kg or just a better quality servo like the savox? 

[Rustypeb89]

Had a little play after work today defiantly think that before I was playing with the needles before the engine got up to its proper temp. This time i richened it quite a lot the HSN was about 7 1/2 turns out and the LSN 3 1/2 so was very boggy to start had to put half a tank through on blocks before it would move with out bogging down and cutting out but after that I drove it around and after 2 more tanks it started leaning its self out so guessing it was getting up to temp about then? Unfortunately it was getting dark by then and had to sort the dog out so had to stop. But at least I think I know how to start the tuning now. 

Hoping I can get my head around it a bit more before this Sunday as hopefully going to go to a local club, unfortunately no one runs nitro there at the moment but they said I'm welcome to have a try on there 1/8th track when there not racing. 

[locky]

14 hours ago, Rustypeb89 said:

HSN was about 7 1/2 turns out

 

Sounds rather rich to me. A really rich engine wont get up to temp very quickly.

[Rustypeb89]

26 minutes ago, locky said:

 

Sounds rather rich to me. A really rich engine wont get up to temp very quickly.

 

Yeah I think it should be too rich but if I lean it a little more it seems to hold the rpm after full throttle. Unless it holding rpm is a LSN issue? 

This engine is confusing me quite a bit, might try and find someone local who might be able to help me with it tho don't know anyone at the moment. But think it would be easier for someone with experience to see it in person then me trying to explain it which I don't do very well. 

 

Edit, to add when I was at your settings the performance was a lot better but seemed to be too lean as it was holding rpm and sounding buzzy after letting go of the throttle, to get rid of that I had to go this rich but now it is very boggy and rough sounding, after a couple of tanks it got up to temp I guess and did lean out. Unfortunately I wasn't able to see what it was like too much after this as I had to stop. 

Edited February 3, 2017 by Rustypeb89

[locky]

Sounds like maybe your LSN/idle need adjusting. Did you reduce the idle gap? If not reduce it further.  If the idle gap is too big, the rpm will not totally drop to where it should be, rather it hangs at the pre-determined point waiting for the LSN to take over and lower it the rest of the way to a good idle.

 

If all else ails go back to stock settings and start again with needles at stock. Tune HSN 1st, get it running up to temp then quickly tune, you should quickly find difference between bogging and screaming at WOT. Then LSN, then idle. Some people use the pinch test to indicate LSN performance. It isnt always reliable but if your engine dies immediately it's too lean if it runs for 10 secs then too rich. Or you see if the engine temps keep reducing at idle after WOT, if they dont then LSN too lean.

 

Or air leak somewhere. Check screws on backplate and cooling head and carb. If you dont have any RTV gasket sealer then get some and apply to carb neck and backplate, reassemble and let it cure overnight.

[Rustypeb89]

Thanks agin locky, think I will go through and rule a few things out so will remove the engine then check for air leaks if there are any will fix them and check again when I'm happy there is non I will put the engine back and re check the idle gap. I have some .3mm wire so will make it a tiny little bit bigger then that so about .5mm. I will then put the needles back to stock tho in the manual it does say there both 3.75 turns out which seems a bit lean for the high end so might start that about 5 turns out and see if I can get it tuned from there. 

Thanks again 

[locky]

More reading....http://www.abergavennymodelcentre.co.uk/nitro-car-engine-tuning.php